One strategy I use to stay calm during the day is.....

Practicing my breathing

Breathe

Paint

Going out and playing games

Read childrens books

Drown everything out with music and keep busy

if a negative thought comes into your head just imagine ur self swerving away from it or kicking / flicking it out the way

breathing exercises :)

Drink water and breathe

Listening to music with my hood on so no one can see because at school they dont want you to listen to music during class. The cord is in my hoodie with one bud out so I can still hear what the teacher is saying. It helps a lot with social anxiety for me